Backer Rod is an easy to compress rope-like celled polypropylene / polyolefin based foam. It is inserted into a clean joint at the required depth before adding caulk / sealant. Backer Rod creates an even depth and supports (back stops) the sealant / caulk allowing it to form the proper shape (about 2x as wide as deep) and also prevents 3 sided adhesion (bond breaker). It is especially important to use it with Self Leveling Expansion Joint Sealants. Very large and Soft Backer Rods are also used for filling gaps and for sealing in general construction.

Note: Backer Rod is inexpensive, but can be expensive to ship. This is because of the large volume of space it takes in boxes. Dimensional weight applies. More information is
here: UPS Dimensional Weight and Oversized Packages

SOFT backer rod is highly compressible and can be easily used at widths as low as 40% of product diameter (lower in small sizes). CLOSED CELL product can be used in all applications where SOFT is specified.

Chemically cross-linked closed cell
Backer Rod is High-Temperature resistant to 410F. Its used for hot-pour, rubber-asphalt, and thermo-plastic sealants. Resistant to gas, oil and most solvents. Commonly used in roadways, runways and airplane hangers. Click here for Product Data Sheet

Click links below to get cost, detailed information and to order products.

Open
Cell Backer Rod is used for hot pour, where out-gassing and bubbling is a problem, or where quicker curing is needed (it enables 2-sided air exposure
on some products). Open Cell foam is enable air to reach both sides of joint. VERY soft and compressible. Resistant to gas, oil and most solvents. For Hot Pour applications, generally the joint is thicker and closer to 1:1 size. Small joints should have at least 3mm (.12" compression), Available in black or yellow color.

Open-cell soft backer rod is highly compressive. It serves as a backing for caulking, sealants and all types of hot pour, chemical sealant and cold sealant products.
It is yellow in color, odorless and chemically inert, made from Polyurethane.

Open cell backer "Denver Foam" rod can take up to 500F during hot applications and is compatible with all types of ASTM D3405, D1956 and C1330 hot pour and chemically cured sealants.

Open cell allows air to reach sealant from BOTH sides during cure, providing a bubble free, faster, more uniform cure.
Open cell construction eliminates out-gassing and cold flow problems sometimes associated with certain materials.
Open cell backer rod can also be "saturated" with sealant and used to "carry" sealant to difficult-to-reach repair areas and to create underwater "plugs" (normally it will not absorb sealant without "working it" in).

Placement & Joint Illustrations:

Tips for Installing / Placing Backer Rod:

When working on any expansion joint, backer rod is used together with the sealant. Including SL1, SL2 self-leveling sealants and with vertical grade sealants. Summmary: Pry out the old joint materials. Clean joint well (wire brush & vacuum etc). Let dry as needed. Vacuum (edges should be clean and have a fresh surface). If edges are not clean, run a grinding disk or blade across them, then vacuum again. Set backer rod as noted. Apply sealant, not thicker than 1/2 the width, measured at the center area. Do not apply sealant above the top plane of the concrete. Tires should not push down on it.

Details:

1. Remove old joint materials. (use pry-bars, screw drivers) . If you have old sealant in it, use one of these to remove: Cut Out Knives

2. Clean joints (wire brush, then sweep, then vacuum). The joint or opening should be clean and dry and free of all contaminates, loose materials and free of water or frost.

b. Where necessary, primer should be applied only to the edges of the joint surface and allowed to dry before Backer-Rod is placed.

DO NOT prime Backer Rod.

4. Install Backer Rod: Lightly compress backer-rod into the joint. Install backer-rod using a blunt tool or a plain faced roller. It should form a seal againt edge of joint to prevent sealant from running out.

Set the rod to the depth recommended by sealant manufacturer, (typically about 1/2 of joint width measured at the crown of the backer rod). A template or roller gauge may be used to control the depth at which the rod is placed.

5. Don't stretch, puncture or tear backer-rod during installation.

6. IMPORTANT NOTE FOR SELF-LEVELING SEALANT APPLICATIONS: All Backer Rod sides, joints and end areas must be completely sealed against a joint surface, otherwise Self Leveling sealants WILL run out of any gaps. Use heavy masking tape to seal ends of joints.

7. Mask areas to protect from tailing or spillage. Best practice is to apply masking tape to all joint edges. Caution: spilled sealant is almost impossible to remove completely. Mask areas before applying sealant.

8. Apply Sealant as required. For driveways or walkways, do not apply up to or above surface level. Self leveling product does not need to be tooled. Others are tooled to shape immediately as required.

How Much Sealant Do you Need?

Tips for Applying Sealants:

1. Where priming of the surface material is necessary, primer should be applied only to the sides of the joint surfaces and allowed to dry tack-free before the Backer-Rod is placed. DO NOT prime the Backer-Rod. Many primers ARE STAINING, be careful where they are applied.

2. Follow suggestions for joint-sealant application as directed by the sealant manufacturer.

3. As needed, tool to desired shape using a caulking tool or old spoon. Hint: For polyurethanes, wet the tool regularly with water or toluene to enable a smooth surface. Soapy water is not recommended as some soaps can interfere with joint bonds.

Our Soft, Closed Celled and Hot Rod backer rod is polyolefin based. A polyolefin is a polymer produced from a simple olefin (also called an alkene with the general formula CnH2n) as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene.Â Polypropylene is another common polyolefin which is made from the olefin propylene.

SOFT Backer Rod Construction Uses:

Soft Backer Rod for residential construction is also commonly used to seal air gaps around wall or joint cavities, between pre-hung doors and windows and rough openings in wood frame homes. The low compression deflection and high compression recovery of these products will not bow windows or door jambs and adapts to seasonal joint movement. Specific uses for Soft Backer Rod includes log homes, marriage joints, sealing at attic access openings, casement window joints, some dry wall applications, wall to wall joints, wall to floor joints, and roof to wall joints, and around doors and windows in wood frame structures.

Compatibility: Our our backer rod products are an inert composition and therefore compatible with all known cold applied sealants including butyl, polysulfide, vinyl acetates, PVA, acrylics, polyurethanes, tri-polymers and silicones. They are chemically inert and will resist oil, gasoline and most other solvents. These materials will not stain nor adhere to sealant materials and are non-exuding. For HOT pour and chemical sealants, use Hot-Rod or the Open Cell Foam. If bubbling / gassing is a problem, Open Cell Foam is best. More Information can be found in the Technical Data Sheets.

EIFS Construction and Joint Design: See the EIFS Guide for details.Â Trouble-free EIFS application is accomplished by forming a 1/2" to 3/4" sealant gap wherever EIFS meets a non-EIFS material, such as roofing, trim, or doors and windows, according to the EIMA EIFS Guide. The correct gap makes it possible to finish the exposed edges of the expanded polystyrene, which should be wrapped with reinforcing mesh before the EPS is secured to the sheathing with a waterproofing application of base coat. Then the rest of the finish goes on. Finally, the gap is filled with soft or closed-cell backer rod and a bead of compatible sealant. Novalink Polyether Sealant is an excellent sealant for this applications. Textured Sealants are also available which cure textured to look stucco-like.